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BISC 221 > Topic 2: Nutrition and the Digestive System > Flashcards

Topic 2: Nutrition and the Digestive System Flashcards

1
Q

What are the four processes in the gastrointestinal (GI) tract?

A
  1. ingestion
  2. mixing
  3. digestion
  4. absorption
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2
Q

What happens in ingestion?

A

foods and liquids are taken into the mouth

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3
Q

What happens in mixing?

A

the smooth muscle in the walls of the GI tract mixes the food and pushes it along

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4
Q

What happens in digestion?

A

food is broken down into its component parts by both mechanical and chemical processes

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5
Q

What happens in absorption?

A

the epithelial cells lining the GI tract absorb the digested food molecules and pass them to the blood

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6
Q

What are the four layers of the GI tract?

A
  1. mucosa
  2. submucosa
  3. muscularis
  4. serosa
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7
Q

What are the functions of the mucosa?

A

functions are secretion and absoprtion

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8
Q

What is the submucosa?

A

thick connective tissue layer; blood and lympth vessels, nerves, and glands

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9
Q

What is the muscularis?

A

the main muscular layer of the tract (smooth muscle)

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10
Q

What layer is responsible for the movement of food?

A

inner circular layer and outer circular layer

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11
Q

What is the serosa?

A

epithelial sheet that covers all the organs and also lines the abdominal cavity

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12
Q

What are the three phases of swallowing?

A
  1. oral
  2. pharyngeal
  3. esophageal
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13
Q

What is the oral phase (voluntary)?

A

tongue consciously moves bolus of food towards the oropharynx

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14
Q

What is the pharyngeal phase (involuntary/structure)?

A
  1. uvula covers nasal activity
  2. epiglottis covers opening to respiratory system
  3. respiratory centers in brainstem are inhibited so you don’t gasp for air while swallowing because trachea is closed
  4. tongue closes off mouth from pharynx. No place for food that go except down the hatch
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15
Q

What is the esophageal phase (involuntary)?

A

peristaltic waves of muscle contractions move food toward the stomach

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16
Q

What are the two sphincter muscles in the esophagus?

A
  1. top: pharyngoesophageal sphincter (upper esophageal sphincter)
  2. bottom: gastroesophageal sphincter (lower esophageal sphincter)
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17
Q

What is the function of the pharyngoesophageal sphincter?

A

ring of muscles that prevents air from entering esophagus–occasionally breached–eructation (burping)

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18
Q

What is the function of the gastroesophageal sphincter?

A

prevents acid from stomach from entering esophagus–occasionally breached–acid reflux (heart burn)

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19
Q

What is the structure of the stomach?

A
  1. J-shaped
  2. bounded by the lower esophageal sphincter and the pyloric sphincter
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20
Q

What are the three parts of the stomach?

A
  1. fundus: above the esophagus
  2. body: main part
  3. antrum: lower part: heavier musculature
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21
Q

What is the volume of the stomach?

A

empty: 50 mL; full: 1 liter

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22
Q

How can the stomach volume range 50 mL-1 liter

A
  1. rugae: folds in mucosa that can be flattened
  2. smooth muscle can be stretched
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23
Q

What is the mechanical function of the stomach?

A

stomach contractions: blend the food and gastric secretions into chyme; chyme is propelled through the pyloric sphincter into the small intestine

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24
Q

What is the chemical function of the stomach?

A

the chyme is mixed with enzymes and acid to begin the process of breaking it into its component parts

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25
Q

Where is gastric juice made?

A

(2-3 quarts per day) made in gastric pits and glads that line the stomach mucosa

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26
Q

What cells make up the gastric pits and glands?

A
  1. mucous neck cells
  2. chief cells
  3. parietal cells
  4. G-cells
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27
Q

What is the function of mucous neck cells?

A

mucus to protect stomach wall from stomach acid

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28
Q

What is the function of chief cells?

A

pepsinogen (breaks down protein) released as inactive precursor

29
Q

What is the function of parietal cells (2)?

A
  1. hydrochloric acid (HCl): kills bacteria and activates pepsinogen
  2. intrinsic factor: aids in the absorption of vitamin B12 (important for RBC maturation). Pernicious anemia-autoimmune attack on parietal cells
30
Q

What is the function of G-cells?

A

gastrin: stimulates chief and parietal cells

31
Q

What are the three phases of the control of gastric digestion?

A
  1. cephalic phase
  2. gastric phase
  3. intestinal phase
32
Q

What happens in the cephalic phase?

A
  1. initiated by the senses
  2. stimulates gastric secretion
33
Q

What happens in the gastric phase?

A
  1. food enters the stomach stimulates the brain to increase gastric secretion
  2. gastrin, produced by G cells stimulates chief and parietal cells
34
Q

What happens in the intestinal phase?

A
  1. if digestion complete: gastric secretion decreased
  2. if digestion incomplete, gastric secretion increased
35
Q

How long is the small intestine?

A

20 feet, the longest digestive organ

36
Q

What are the three regions of the small intestine?

A
  1. duodenum
  2. jejunum
  3. ileum
37
Q

What is the function of the duodenum?

A

(10 inches) digestion

38
Q

What is the function of the jejunum?

A

(8 feet) absorption of sugars, fatty acids and amino acids

39
Q

What is the function of the ileum?

A

(11.5 feet) absorption of vitamin B12 and bile ducts

40
Q

What are the three levels of folding in the mucosa?

A
  1. circular folds
  2. villi
  3. microvilli (brush border)
41
Q

What does mucosa layer folding cause (3)?

A
  1. increased surface area
  2. churning
  3. increased time to digest and absorb nutrients
42
Q

The villus is connected to what two systems?

A

blood stream and lymphatic system

43
Q

What is the mechanical digestion of chyme?

A

segmentations allow chyme to interact with the mucosa layer: food moves back and forth as it is pushed along

44
Q

What is the chemical digestion of chyme?

A

digestive juices contain enzymes added to chyme to further break down macromolecules

45
Q

What are the macromolecules for chemical digestion of chyme (3)

A
  1. carbohydrates
  2. proteins
  3. fats
46
Q

What are the types of carbohydrates?

A
  1. lactase (lactose)
  2. sucrase (sucrose)
  3. maltase (maltose)
  4. amylase (starches)
47
Q

What are the types of proteins?

A

proteases: trypsin and chymotrypsin

48
Q

What are the types of fats?

A

lipase

49
Q

Where are carbohydrates produced?

A

all but amylase produced by the cells of the small intestine; amylase produced by the pancreas

50
Q

Where are proteins produced?

A

produced by the pancreas

51
Q

Where are fats produced?

A

produced by the pancreas

52
Q

Where do nutrients from chyme move?

A

into the villi and enter the bloodstream

53
Q

What is the function of accessory organs?

A

aid in digestion and absorption of nutrients?

54
Q

What are the four accessory organs?

A
  1. salivary glands
  2. pancreas
  3. gall bladder
  4. liver
55
Q

What is the function of the salivary glands?

A

produce amylase to digest starches

56
Q

What is the function of the pancreas (4)?

A
  1. digestive enzyme factor buffers the acidity of chyme
  2. secretes enzymes (proteases, amylase, lipase)
  3. produces bicarbonate
  4. delivers products to duodenum via ducts
57
Q

What is the function of the gall bladder (3)?

A
  1. stores bile: aids in fat digestion
  2. stores and concentrates bile
  3. delivers bile to the duodenum via the common bile duct
58
Q

What is the function of the liver (2)?

A
  1. removes toxins and impurities from the bloodstream
  2. produces bile
59
Q

What is bile?

A

water, cholesterol, bile salts, lecithin, and pigments

60
Q

What is the direction of nutrients to the liver?

A

blood carrying nutrients away from the intestine and stomach travels directly to the liver in the hepatic portal vein; other veins collect and drain into the vena cavae

61
Q

What vein carries blood to the liver?

A

hepatic portal vein

62
Q

What does the special vascular arrangement in the liver allow?

A

digested molecules can be “screened” for toxins by the liver

63
Q

What happens to the hepatic portal vein in the liver?

A

breaks up into a second bed of capillaries called liver sinusoids that gets blood from the hepatic artery

64
Q

What happens to blood after it leaves the capillaries?

A

returns to the heart

65
Q

What is the function of the large intestine?

A
  1. removes almost all the water from the chyme
  2. absorption of electrolytes (ions)
  3. form and store feces; evolved for good reason to keep away predators
66
Q

Ileocecal sphincter has a _ valve

A

one-way

67
Q

What opens the sphincter?

A
  1. pressure in small intestines causes relaxation and opening
  2. gastrin released in response to food in the stomach and intestine
68
Q

What closes the sphincter?

A

pressure in the large intestine pushes the valve closed and prevents bacteria from entering small intestine

BISC 221 (10 decks)

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